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cpan/Math-BigInt-FastCalc/t/biglog.t  view on Meta::CPAN

# versions up to v1.63, and for bsqrt($x) when $x << 1 for instance).

use strict;
use warnings;

use Test::More tests => 73;

use Math::BigFloat only => 'FastCalc';
use Math::BigInt;

my $class = "Math::BigInt";

###############################################################################
# test $n->blog() in Math::BigInt (broken until 1.80)

is($class->new(2)->blog(),    '0', "$class->new(2)->blog()");
is($class->new(288)->blog(),  '5', "$class->new(288)->blog()");
is($class->new(2000)->blog(), '7', "$class->new(2000)->blog()");

###############################################################################
# test $n->bexp() in Math::BigInt

is($class->new(1)->bexp(), '2',  "$class->new(1)->bexp()");
is($class->new(2)->bexp(), '7',  "$class->new(2)->bexp()");
is($class->new(3)->bexp(), '20', "$class->new(3)->bexp()");

###############################################################################
# Math::BigFloat tests

###############################################################################
# test $n->blog(undef, N) where N > 67 (broken until 1.82)

$class = "Math::BigFloat";

# These tests can take quite a while, but are necessary. Maybe protect them
# with some alarm()?

# this triggers the calculation and caching of ln(2):
is($class->new(5)->blog(undef, 71),
   '1.6094379124341003746007593332261876395256013542685177219126478914741790',
   "$class->new(5)->blog(undef, 71)");

# if the cache was correct, we should get this result, fast:
is($class->new(2)->blog(undef, 71),
   '0.69314718055994530941723212145817656807550013436025525412068000949339362',
   "$class->new(2)->blog(undef, 71)");

is($class->new(11)->blog(undef, 71),
   '2.3978952727983705440619435779651292998217068539374171752185677091305736',
   "$class->new(11)->blog(undef, 71)");

is($class->new(21)->blog(undef, 71),
   '3.0445224377234229965005979803657054342845752874046106401940844835750742',
   "$class->new(21)->blog(undef, 71)");

###############################################################################

# These tests are now really fast, since they collapse to blog(10), basically
# Don't attempt to run them with older versions. You are warned.

# $x < 0 => NaN
is($class->new(-2)->blog(),    'NaN', "$class->new(-2)->blog()");
is($class->new(-1)->blog(),    'NaN', "$class->new(-1)->blog()");
is($class->new(-10)->blog(),   'NaN', "$class->new(-10)->blog()");
is($class->new(-2, 2)->blog(), 'NaN', "$class->new(-2, 2)->blog()");

my $ten = $class->new(10)->blog();

# 10 is cached (up to 75 digits)
is($class->new(10)->blog(),
   '2.302585092994045684017991454684364207601',
   qq|$class->new(10)->blog()|);

# 0.1 is using the cached value for log(10), too

is($class->new("0.1")->blog(), -$ten,
   qq|$class->new("0.1")->blog()|);
is($class->new("0.01")->blog(), -$ten * 2,
   qq|$class->new("0.01")->blog()|);
is($class->new("0.001")->blog(), -$ten * 3,
   qq|$class->new("0.001")->blog()|);
is($class->new("0.0001")->blog(), -$ten * 4,
   qq|$class->new("0.0001")->blog()|);

# also cached
is($class->new(2)->blog(),
   '0.6931471805599453094172321214581765680755',
   qq|$class->new(2)->blog()|);
is($class->new(4)->blog(), $class->new(2)->blog * 2,
   qq|$class->new(4)->blog()|);

# These are still slow, so do them only to 10 digits

is($class->new("0.2")->blog(undef, 10), "-1.609437912",
   qq|$class->new("0.2")->blog(undef, 10)|);
is($class->new("0.3")->blog(undef, 10), "-1.203972804",
   qq|$class->new("0.3")->blog(undef, 10)|);
is($class->new("0.4")->blog(undef, 10), "-0.9162907319",
   qq|$class->new("0.4")->blog(undef, 10)|);
is($class->new("0.5")->blog(undef, 10), "-0.6931471806",
   qq|$class->new("0.5")->blog(undef, 10)|);
is($class->new("0.6")->blog(undef, 10), "-0.5108256238",
   qq|$class->new("0.6")->blog(undef, 10)|);
is($class->new("0.7")->blog(undef, 10), "-0.3566749439",
   qq|$class->new("0.7")->blog(undef, 10)|);
is($class->new("0.8")->blog(undef, 10), "-0.2231435513",
   qq|$class->new("0.8")->blog(undef, 10)|);
is($class->new("0.9")->blog(undef, 10), "-0.1053605157",
   qq|$class->new("0.9")->blog(undef, 10)|);

is($class->new("9")->blog(undef, 10), "2.197224577",
   qq|$class->new("9")->blog(undef, 10)|);

is($class->new("10")->blog(10, 10), "1.000000000",
   qq|$class->new("10")->blog(10, 10)|);
is($class->new("20")->blog(20, 10), "1.000000000",
   qq|$class->new("20")->blog(20, 10)|);
is($class->new("100")->blog(100, 10), "1.000000000",
   qq|$class->new("100")->blog(100, 10)|);

is($class->new("100")->blog(10, 10), "2.000000000",     # 10 ** 2 == 100
   qq|$class->new("100")->blog(10, 10)|);
is($class->new("400")->blog(20, 10), "2.000000000",     # 20 ** 2 == 400
   qq|$class->new("400")->blog(20, 10)|);